When liquids are being handled in a terrestrial laboratory, the force of gravity generally causes the liquids to accumulate at the bottom of a container. Gasses such as air, being generally less dense than the liquids, tend to rise to the top of the container. Thus, for example, containers or other components of a fluid-handling system may be designed to take advantage of these effects. For example, structures to vent air bubbles or generated gasses may be placed at the top of the container.
Also, in a terrestrial setting, it may be expected that components of a fluid-handling system will be accessible for cleaning or other servicing or maintenance. Thus, when a component of the system requires maintenance, the component could be removed from the system for handling.
In some cases, effects of gravity in a terrestrial laboratory may interfere with the experiment or other process that are being performed in the laboratory or being developed. In such cases, a system may be placed in microgravity environment. When a system is in a microgravity environment, all components of the system are subject to identical or indistinguishable gravitational forces. For example, the system may be in free fall or in orbit about a massive body. In the microgravity environment, gravitational contact forces between two components of the system, or weight, may be absent or negligible.
A microgravity environment may include a drop tower or similar facility, producing a few seconds of microgravity. Up to about half a minute of continuous microgravity may be provided by an aircraft that is flying in an appropriate pattern (e.g., parabolic arcs). A manned or unmanned spacecraft in earth orbit or deeper space may enable long (e.g., days or longer, and in some cases, unlimited) time in microgravity.
In some cases, a system for performing the process in microgravity may utilize lab-on-a-chip technology or other micro-technology. Use of such technology may enable incorporation of the microgravity system in a platform where available space may be very limited or expensive.
Some such processes require use of liquid materials. A process may require transfer of a liquid from a reservoir to another part of the system, e.g., where the liquid interacts with another component. A process may require transfer of a liquid from the system to a reservoir where the liquid is stored for later use, study, or recovery, or where a waste liquid is stored for later disposal. Typically, a flexible liquid reservoir, e.g., in the form of a bag or pouch, enables storage of liquids in a manner that prevents escape of the liquid, conserves space, and enables transfer of the liquid without trapping air or gases which could lead to formation of bubbles.
Due to the weightlessness in the microgravity environment, liquids do not accumulate at the bottom of a container but may float freely within a container or conduit. A fluid-handling system for microgravity must be able to operate under such weightless conditions.